The inventor herein has secured several U.S. patents bearing upon the general field of the invention, as follows, which are cited for general background purposes:
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Many of these patents rely upon the employment of corner truss brackets which are installed proximate the roof-rib corner junction areas. Upwardly and outwardly angulated mine roof bolts secure the brackets in place, and the roof bolts are placed under substantial tension by tightening nuts as well as by tie rod or other trussing structure which is connected to the brackets and also placed in tension. When in active mode, that is, when the over-all truss is placed in tension, then a true truss effect is imposed on mine roof strata, placing the same in compression and thus deterring the falling down or essential dilation of the mine roof. This is produced by the resultant upwardly and inwardly directed force vectors, generated at the brackets, which are directed upwardly in the strata inwardly of the brackets. This is a highly preferred way of supporting mine roofs, for example. But this approach is expensive.
For certain types of strata conditions, it may well be desirable to utilize a support system which is less expensive, and yet will operate quite satisfactorily where extreme conditions are not encountered. Thus, where the corner brackets can be eliminated and the pre-tensioning of the anchor bolts omitted, expense is measurably reduced. This tack leads to a sling approach, whether in active or passive mode: this is to say, whether the sling is actively placed in tension initially, or whether the tension is produced through the dilation downwardly of the mine roof surface. A sling has been conceived in the mining art, see U.S. Pat. No. 5,193,940 (Long). However, such a sling, it is submitted, subjects the connecting structure and/or one or more of its component parts to failure or even fracture. Such is chanced by the generally non-coaxial nature of the coupling structure, as by rods utilized which are not coaxial as herein, but rather are coupled together in a pronounced off-center condition. This results in the generation of force couples which tend to warp and even shear or otherwise fracture portions of the connecting structure. The present invention avoids these difficulties.